As a bonus action, you can draw on a reservoir of life essence to empower yourself for 1 minute, or until you use this feature again. For the duration, you gain one of the following benefits of your choice:
Overgrowth. When you choose this benefit, and as a bonus action on subsequent turns while the benefit lasts, you can expend and roll one Hit Die. You regain a number of hit points equal to the number rolled plus your spellcasting ability modifier.
Withering Strike. When you deal damage, you can change the damage type to necrotic, and you ignore resistance to necrotic damage.
You can use this feature a number of times equal to your proficiency bonus, and you regain all expended uses when you finish a long rest.